OHAPTBE VII.
TRUE SOAP GREASES.
THE soap greases, properly so called, are prepared with
ordinary soft soap (a compound of potash with fatty acids),
or from fats and potash, these forming the emulsions already
referred to. Although these greases are occasionally very
useful, their employment is restricted, owing to the risk that
lack of care in their preparation may leave appreciable quan-
tities of potash or caustic alkali uncombined, with consequent
liability to injury of the metal, which may be extensively
corroded.
Ghardons Soap Grease:—
Soft soap.........10-50
Lye or water ........ 90-50
This peculiar lubricant, which is claimed to specially
lessen the wear and tear of the bearings—a claim which if it
were tenable would be highly commendable—is, according to
its inventor, much cheaper than oil. The proportions of soap
and water vary with the season.
The use of lye, however, for dissolving the soap, appears
objectionable, if only for the reason that caustic alkalis exert
a corrosive action on some metals and metallic alloys—bronze,
for instance—of which machine parts are generally made.
In a properly made soap there is no free fatty acid, so that
any added caustic alkali acts on the metal and soon causes it to
corrode. That Chardon's grease is of little value is shown by
the circumstance that, according to the recipe, it is immaterial
whether water or lye be taken. Any one possessing even
a slight knowledge of chemistry will know what a wide
difference exists between a lubricant consisting of soap and
water and one containing soap and lye.
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